Influência da somatotropina recombinante bovina sobre padrões reprodutivos e metabólicos de éguas submetidas a transferência de embrião

Abstract

The action of r-bST is poorly described in equines, and this research evaluated its influence on follicular dynamics, embryo collection, follicular vascularization and metabolic profile. Ten mares were submitted to daily transrectal ultrasonography evaluation during the interovulatory interval, with only follicles ≥ 5 mm being evaluated, and blood Doppler ultrasonography was performed every 48 hours. Five mares were treated with 500 mg of r-bST at the first and 14th day post ovulation, and other five mares were treated with saline, forming the treated (TG) and control (CG) groups, respectively. When the follicle reached the diameter ≥40 mm, the ovulation was induced with hCG, insemination was performed after 24 hours and embryos collected six days after ovulation. In the first experiment the data were grouped according to the follicular diameter in the phases of emergence, divergence, dominance, preovulatory, induction, insemination and ovulation, all mares being used twice, respecting the interval of two estrous cycles, between repetitions. In the second experiment were evaluated the follicular diameter and follicular vascularization percentage, considering only the moments of the second use of the mares. Concentrations of IGF-I, NEFA, glucose and total protein were measured at all times, with the exception of IGF-I which was evaluated only at the first, sixth, 14th and last day of the interovulatory interval. The TG showed precocious follicular growth (3 days) for the emergence, divergence, dominance and pre-ovulatory phases, as well as for its major subordinate follicle, which began its growth early. The embryo recovery rate was 90% for the GC and 70% for the TG, with 16 structures being collected, obtaining an unfertilized and as another between morula and initial blastocyst for the CG group and morula and compact morula for the GT, with quality of excellent (two groups) to poor (only CG). The TG presented higher percentage of vascularized follicle wall, at the eighth day post ovulation, even without significant differences in the vascularization rates. The concentrations of IGF-I and NEFA showed significant increase in D6 and D14 for IGF-I and D16 for NEFA, but remained within physiological levels. Glucose and total protein concentrations remained constant. It was concluded that r-bST influenced the follicular dynamics of the mares, leading to an anticipation of follicular development and improving the follicular wall vascularization, keeping the body homeostasis, and can be used for reduce the estrous cycle period.